1. Field of the Invention
The invention relates to a tool holder, in particular for a chisel hammer and/or rotary hammer.
2. Description of the Prior Art
For receiving and axially locking drilling or chiseling tools in percussively operated power tools, various tool holders are known. Tool holders of the kind described among other places in German Patent Disclosure DE 10 2005 015100 A1 have a tool receptacle for receiving a cylindrical shaft, introduced through an insertion opening, of a tool insert. In the cylindrical circumferential surface of the shaft, two diametrically opposed detent indentations are provided. The tool holder also has a locking device, which includes a locking element, a blocking element, and a restoring element.
Locking of the tool insert in the tool receptacle is done automatically upon insertion. Here the locking element is displaced axially, counter to the restoring element acted upon by restoring force—usually implemented by a prestressed restoring spring—in the direction of the housing of the power tool until such time as it can deflect radially behind the blocking element into a deflection chamber defined by the restoring element. As the tool insert is pushed in farther, the locking element can then plunge radially into one of the detent indentations provided for it in the shaft of the tool insert and is thrust again in the axial direction to beneath the blocking element by the axially prestressed restoring element.
By axial displacement of the blocking element away from the position of repose defined by the restoring force and a contact face, the locking element can emerge radially from the detent indentation, so that the tool insert can be removed from the tool receptacle by pulling on the tool insert.
In all operating states, the tool locking means must ensure a secure hold of the tool insert in the tool receptacle.
Particularly at the transition from the hammering state to the idling state of the power tool, strong forces on the tool axis defined by the tool insert and oriented in the direction away from the power tool occur, which speed up the tool insert. This thus-caused sudden motion of the tool insert must be absorbed by the locking element and the motion must be stopped. In the process, the locking element is subjected to both axially and radially heavy loads.
Because of the constantly increasing hammering power of power tools, the thus-increasing loads on the locking element cause accelerated wear to components of the locking device—particularly of the locking element. Because of the sudden type of load, the vibratable locking device is additionally caused to vibrate, and the vibration adversely affects the load distribution.